# std::codecvt<InternT,ExternT,StateT>::always_noconv, do_always_noconv

From cppreference.com
< cpp‎ | locale‎ | codecvt

Defined in header `<locale>` |  |
| (1) |
public: bool always_noconv() const throw(); |  | (until C++11)
public: bool always_noconv() const noexcept; |  | (since C++11)
| (2) |
protected: virtual bool do_always_noconv() const throw(); |  | (until C++11)
protected: virtual bool do_always_noconv() const noexcept; |  | (since C++11)

1) Public member function, calls the member function `do_always_noconv` of the most derived class.
2) Returns true if both do_in() and do_out() return `std::codecvt_base::noconv` for all valid inputs.

### Return value

true if this conversion facet performs no conversions, false otherwise.

The non-converting specialization std::codecvt<char, char, std::mbstate_t> returns true.

### Notes

This function may be used e.g. in the implementation of std::basic_filebuf::underflow and std::basic_filebuf::overflow to use bulk character copy instead of calling std::codecvt::in or std::codecvt::out if it is known that the locale imbued in the std::basic_filebuf does not perform any conversions.

### Example

Run this code

    #include <iostream>
    #include <locale>

    int main()
    {
        std::cout << "The non-converting char<->char codecvt::always_noconv() returns "
                  << std::boolalpha
                  << std::use_facet<std::codecvt<char, char, std::mbstate_t>>(
                        std::locale()
                     ).always_noconv() << '\n'
                  << "while wchar_t<->char codecvt::always_noconv() returns "
                  << std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
                        std::locale()
                     ).always_noconv() << '\n';
    }

Output:

    The non-converting char<->char codecvt::always_noconv() returns true
    while wchar_t<->char codecvt::always_noconv() returns false

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